Abstract
Purpose: :
Soft contact lens (SCL) wear induces corneal hypoxia and may decrease the corneal thickness and the cornea keratocyte count. The purpose of this study was to determine whether physiological changes resulting from SCL wear affect the visual outcome of LASIK.
Methods: :
One hundred fifty–six eyes that received CustomVue LASIK to correct high myopia as part of an FDA clinical trial were studied retrospectively. Data were taken from 6–month post–op exams. Pre–operatively, 131 eyes used SCLs, and 25 eyes used spectacles (Spec). Patterns of SCL wear were evaluated, including length of wear, daily wear time, and frequency of overnight use. Visual outcomes, such as refractive error, visual acuity, high order aberrations (HOAs), and contrast sensitivity under different lighting conditions were examined, as well as age, gender, race, corneal curvature, pupil size, and corneal thickness.
Results: :
Before surgery both groups had similar spectacle plane RX s (Spec,–7.86 DS; and SCL, –7.97 DS); similar best corrected visual acuity (–0.06 logMAR for both) and similar contrast sensitivities. After surgery, t–test statistical tests revealed significant differences (p<0.05) between the Spec group and the SCL group. The SCL group had less post–op spherical RX (Spec, +0.35 DS; SCL –0.03 DS) and better photopic contrast sensitivity (Spec, 1.27 logCS; and SCL, 1.34 logCS). Multivariate regression to investigate the impact of SCL–wearing patterns on visual outcomes showed the following: residual refractive error is inversely related to pre–op corneal thickness and frequency of sleeping in contact lenses; pre–op refractive error correlates positively with number of months of contact lens wear; pre–op refractive error does not correlate with post–op residual error; pre–operative refractive error correlates inversely with corneal thickness; contrast sensitivity results correlate minimally with SCL–wearing patterns; and the best predictors for post–op HOAs were pre–op HOAs.
Conclusions: :
Wearing SCLs affects the refractive outcome of LASIK. It is likely that SCL wearing patterns caused changes in corneal physiology, including reduced keratocyte count and stromal thinning, which influenced corneal wound healing and biomechanical response. SCL wearing patterns have a minimal effect on contrast sensitivity and HOAs.
Keywords: cornea: clinical science • contact lens • refractive surgery: LASIK